1. Field of Invention
Apparatuses and methods consistent with the present invention relate to a copy protection method, a CableCARD module, and a video system according to a predetermined digital cable broadcasting standard, and more particularly, to a copy protection method, a CableCARD module, and a video system which prevent a copy protection value of a digital cable broadcasting standard for content of an identical digital cable broadcasting channel in a channel changing operation from not being exchanged.
2. Description of the Related Art
Recently, the use of digital terrestrial television broadcasting and digital satellite broadcasting as broadcast mediums has increased rapidly all over the world.
Digital cable broadcasting standards include the OpenCable standard which is used in America, Korea and elsewhere, the Digital Video Broadcasting-Cable (DVB-C) standard which is used in Europe, and the Integrated Service Digital Broadcasting-Cable (ISDB-C) standard which is used in Japan.
Of these standards, the OpenCable standard is based on the Moving Picture Experts Group-2 (MPEG-2) and the Data Over Cable Service Interface Specification (DOCSIS), which is used as a transmission standard of a cable modem. The OpenCable standard is a set of interface standards for a digital device such as a Set Top Box and digital television which are manufactured in accordance with the OpenCable specifications, as defined by Cable Television Laboratories, Inc.
The OpenCable standard specifies a separate conditional access part and receiving device (i.e., the television, the Set Top Box). Therefore, to satisfy Federal Communications Commission (FCC) regulations in the OpenCable standard, a Set Top Box includes of a video device (host) without the conditional access part and a CableCARD module which includes the conditional access part.
Hereinafter, a copy protection system of matching copy protection values between the video device and the CableCARD Module in the OpenCable standard will be described as follows. The OpenCable standard is embodied with two types of anti-copy systems.
One type of anti-copy system is the Conditional Access System (CAS) for a digital cable broadcast distribution system, and the other type is a Copy Protection System (CPS), which operates between the CableCARD module which is separated from the video device (host) and the video device. Generally, the anti-copy system refers to the CPS.
The existing digital broadcasting receiving device system has a function in which coded contents are received from the distribution system and the coded contends are selectively restored to a common video signal inside the receiving device, (i.e., an Embedded Conditional Access system). The CableCARD module operates as a security module which separates the conditional access function from the receiving device.
In CPS, encoded digital content, which is sent from distribution system, is decoded at the CableCARD module which is used as a subscriber receiving device, (i.e., a CA Payload Decryption) and the digital content is thus converted to a decoded form. Subsequently, the digital content is again encoded by CableCARD module according to the CPS standard (i.e., a CP Encryption), and the encoded content is then transmitted to the video device for reproduction. With such a coding scheme, CPS restricts the use of content which is transmitted from the CableCARD module to the video device.
CPS provides for different levels of copy protection based on the type of content which is received. For instance, no restriction may be placed on public channels which are received, while premium channels may include restrictions on copying the broadcast content.
The application standard of coding for the copy protection is given to a content producer which provided the appropriate content. The information, which determines whether the CPS is allowed or not, is referred to a Copy Control Information (CCI) value, and the CableCARD module of the receiver receives the CCI value corresponding to the transported digital content. Herein, the distribution system transports a message, which indicates whether the receiver is allowed to reproduce the premium digital contents with Private Section data in the MPEG-2 Transport Stream.
Therefore, the video device and the CableCARD module control whether the video device which receives the digital content of a particular broadcast channel can be copied or not based upon the CCI value exchange.
FIG. 1 illustrates an Encryption Mode Indicator (EMI) of the CCI value according to the OpenCable standard. As shown therein, content with a CCI value of “00” is not restricted in the number of copies that can be made, content with a CCI value of “01” restricts copying to two or more generations, content with a CCI value of “10” restricts copying to only one generation, and content with a CCI value of “11” is restricted from the making of any copies.
FIG. 2 illustrates a process of exchanging CCI values between the video device and the CableCARD module according the OpenCable standard.
At operation S20, a channel change request is received by the video device and then the channel is changed. Next, at operation S21, the video device determines whether the channel which corresponds to change channel request is a digital broadcasting channel. At operation S26, in a case where the requested channel is not a digital broadcasting channel, that is, in case where the channel is changed to an analog broadcasting channel, the channel change operation ends without the CCI value exchange.
Meanwhile, in a case where the channel is changed to a digital broadcasting channel, at operation S22, the CableCARD module transports a Request_CCI_Exchange message to the video device. At operation S23, the video device which receives the Request_CCI_Exchange message transports a Request_CCI_N_host message to the CableCARD module in response to the Request_CCI_Exchange message.
At operation S24, in a case where the Request_CCI_N_host message is received from the video device, the CableCARD module transports an Authentication CCI message to the video device, and at operation S25, the video device determines the CCI value from the Authentication CCI message which is received. Therefore, at operation S26, the channel change operation is finished. Accordingly, the video device controls whether the content of the selected digital broadcasting channel may be copied or not according to the CCI value which is determined.
Herein, in a case where the CCI value of the appropriate digital broadcasting channel is not received by the video device for any reason in the process where the video device changes to the digital broadcasting channel, the OpenCable standard indicates that the video device sets the CCI value of the digital broadcasting channel to a “11” value. That is, no copying is allowed of the content of the digital broadcasting channel if the video device does not receive the CCI value.
Various technical features related to the copy protection according to the OpenCable standard have been disclosed. For example, a conditional copy free with respect to a copy free is disclosed in Japan Patent first Publication No. 2004-7494, and coding of appropriate information and receiving and sending of coded information in the exchange of the CCI value are disclosed in PCT International Publication No. 2001-5150.
However, in OpenCable standard environments, in a case where the user changes the channel from an analog broadcasting channel to a digital broadcasting channel while viewing the analog broadcasting channel, there is a case that the CCI value exchange with respect to the digital broadcasting channel is not accomplished. Particularly, in case where the user changes the channel to the analog broadcasting channel while viewing the digital broadcasting channel, and the user converts the channel back to the former digital broadcasting channel, the error occurs because the CCI value exchange is not accomplished.
Therefore, copying content of a channel may be improperly restricted because the CCI value exchange does not occur due to the channel change operation from an analog channel to a digital channel.
Further, the user may recognize that the copying of the content of the digital broadcasting channel should be allowed and may therefore misconceive a copy error of the video device or the CableCARD module.